Hydroprocessing can include processes which convert hydrocarbons in the presence of hydroprocessing catalyst and hydrogen to more valuable products.
Hydrotreating is a hydroprocessing process used to remove heteroatoms such as sulfur and nitrogen from hydrocarbon streams to meet fuel specifications and to saturate olefinic or aromatic compounds. Hydrotreating can be performed at high or low pressures, but is typically operated at lower pressure than hydrocracking.
Hydrocracking includes processes which convert hydrocarbons in the presence of hydrocracking catalyst and hydrogen to more valuable products. Hydrocracking is a hydrocracking process in which hydrocarbons crack in the presence of hydrogen and hydrocracking catalyst to lower molecular weight hydrocarbons. Depending on the desired output, the hydrocracking reactor may contain one or more beds of the same or different catalyst. Hydrocracking is a process used to crack hydrocarbon feeds such as vacuum gas oil (VGO) to diesel including kerosene and gasoline motor fuels.
Hydrocarbon feed to a hydrocracking unit can be pretreated with hydrotreating catalyst to remove heteroatoms from the hydrocarbon molecules and to saturate aromatics. Hydrocarbon feed streams to hydrocracking units can often contain significant proportions of desired product such as diesel. If precautions are not taken, the diesel can be hydrocracked to naphtha which may not be desired by the refiner.
There is a need, therefore, for improved processes and apparatuses that preserve diesel in the hydrocracking unit.